Night Vision Goggle (NVG) Warship Lighting

Landing a helicopter on the flight deck of a ship is a difficult task at the best of times. Now imagine doing it in the dark, with the ship moving. The difficulties become greatly multiplied.

The use of night vision goggles (NVGs) is well established as a key technology to help aircrew operate at night. Pilots use NVGs to enhance their operations and to improve flight safety. Ideally they would like to use them throughout the flight envelope, including take off and recovery to the flight deck. Switching between aided and unaided flight is undesirable as the eye must adapt rapidly.

However, lights must be adapted to work with NVGs. Cockpit lighting modifications are routine and standards and techniques have been well known for many years. Typically they involve adding special filters to all cockpit light sources to remove near infra-red wavelengths so that NVGs can operate without interference. This is known as NVG compatible lighting.

What is less well known is that the ship lighting can also be modified, and this can be done relatively easily and cost effectively. Unmodified ship lighting can seriously impact the pilot’s view of the flight deck. Filament lamp sources are a particular problem as they emit a high proportion of infra-red – the very wavelengths that interfere most with NVGs. Large halos appear around each light source, including from reflections off the sea surface, glare effects appear across the field of view, and the sensitivity (gain) of the goggles is reduced. The performance of the NVGs is seriously affected and safety of flight is impacted as a result.

This is illustrated in Figure 1, showing the flight deck of an aircraft carrier where most of the lighting has been modified to NVG compatibility, but the unmodified stern light is creating major problems.

There are three main functions for the ship lighting and different requirements for NVG modification apply to each.

Some lights are used to guide and inform aircrew during flight operations. These include flight deck marker lights, flood and wash lights, deck status lights, horizon indicators, and obstruction and warning lights. These broadly fall into the category of visual landing aids (VLAs). In this case the lights need to be seen by the aircrew through their NVGs, so a fine balance between reducing interference and maintaining visibility is required.

Other lights are for the benefit of the ship’s crew, who need good illumination to perform their routine tasks safely. These include general illumination, both internal and external, lights for special functions such as RAS floodlighting, and instrument indicator and display lights. These usually don’t need to be seen by aircrew through NVGs and so need to be made more NVG compatible.

Then there are also the lights that are required by law to be shown, i.e. navigation lights. Here the issue is to maintain legally required colours and brightness levels while enhancing levels of NVG compatibility.

Any and all of these light types if left unmodified can affectNVG operation. 

Consolite Technology has worked on NVG compatible lighting for around 30 years, first on aircraft lighting and more recently on ship lighting. Consolite is at the forefront of techniques for warship NVG lighting, and wrote the world’s only whole ship standard defining lights for use with NVGs.

There are two possible approaches –existing lights can be modified, or new lights can be provided.

Consolite offers both approaches. The modification route typically starts with a ship survey to identify all applicable lights and, with key ship’s staff, an assessment of their function to determine the appropriate modification. In many cases this simply involvesadding a filter, usually to replacean existing window in the light housing.This means that there is no need for rewiring and it can often be done in situ. It can also be done without affecting the mechanical or environmental integrity of the light. 

The fit can easily be integrated into a routine scheduled maintenance operation, or can be offered as a special fit without significantly affecting mission readiness. On new build ships filter upgrade kits are often supplied to the shipyard or the electrical system integrator for incorporation into previously procured conventional lights.

Consolite has upgraded many ships around the world using this technique, including aircraft carriers, LPDs, LPHs, LSLs, frigates, destroyers, OPVs and landing craft, so it is very well tried and tested. It is also a very cost effective approach that creates minimal disruption to existing systems.

An example is seen in Figure 2, showing an OPV modified by Consolite with fluorescent lights and floodlights all filtered for NVG compatibility. Figure 3 shows a typical filter assembly developed for a simple retrofit to an existing light unit.

More recently Consolite has developed its own range of dual mode luminaires for general illumination on ships. These include surface mounted lights, flush mounted lights and floodlights. All are based on LEDs and offer two modes - normal lighting and a switchable NVG compatible mode. The arrangement of LEDs and the design of the drivers mean they are electrically very robust, ensuring long life and high fault tolerance. In addition to the benefits of having an NVG mode available they also offer significant benefits when it comes to reduced maintenance activities and lower power consumption.

These lights are currently entering service on various ships in the UK and elsewhere. 

Figure 4 shows an example of an LED floodlight. This offers dual mode NVG compatible operation, as well as the other benefits arising from use of LEDs such as high reliability and high efficiency.